COMPARISON BETWEEN FLEXIBILITY-BASED AND STIFFNESS-BASED NONLINEAR BEAM-COLUMN ELEMENTS

Flexibility-based and stiffness-based fiber-model beam-column elements are investigated in this paper. Flexibility-based beam-column elements are based on force interpolation functions that reproduce the variation of internal element forces in a strict sense in the absence of geometric nonlinearity. Numerical examples and tests of reinforced concrete columns under biaxial bending have been selected for computational effectiveness comparison between the two methods and verification of fiber model beam-column elements. The results show that flexibility-based beam-column element are apparently superior to stiffness-based beam-column element in dealing with softening problems of structures in strong nonlinear phase. Fiber model beam-column elements are presently one of the most practical and efficient element models handling biaxial bending and variable axial force coupling problems of frame structures.